I'm trying to using Slick to interact with Oracle DB. The mapping is:
trait EntityTable extends DataBaseConfig{
import driver.api._
class Log(tag: Tag) extends Table[LogEntity](tag,"LOG_SCHEMA.A_TABLE_WITH_VERY_LONG_NAME") {
def id = column[Option[Long]]("LOG_ID",O.PrimaryKey,O.AutoInc)
def log = column[String]("LOG_TEXT")
def * = (LOG_ID, LOG_TEXT) <> ((LogEntity.apply _).tupled, LogEntity.unapply)
}
protected val getLogs = TableQuery[Log]
}
From the debugger I see the SQL generated is:
select "LOG_ID", "LOG_TEXT" from "LOG_SCHEMA.A_TABLE_WITH_VERY_LONG_NAME"
This gives me an
ORA-00972: identifier is too long
How can I have slick generates query without double quotes? Or is there a better way to deal with long table name in different schemes which I do not have control over? Thanks!
In Oracle you can not have names (table, index, view) longer than 30 characters. In your example I guess you have a mistake, instead of
"LOG_SCHEMA.A_TABLE_WITH_VERY_LONG_NAME"
try this:
"""LOG_SCHEMA"."A_TABLE_WITH_VERY_LONG_NAME"""
or this:
"\"LOG_SCHEMA\".\"A_TABLE_WITH_VERY_LONG_NAME\""
It does not matter how the table has been created A_TABLE_WITH_VERY_LONG_NAME can not have more than 30 characters.
Related
I have something like this, using Akka, Alpakka + Slick
Slick
.source(
sql"""select #${onlyTheseColumns.mkString(",")} from #${dbSource.table}"""
.as[Map[String, String]]
.withStatementParameters(rsType = ResultSetType.ForwardOnly, rsConcurrency = ResultSetConcurrency.ReadOnly, fetchSize = batchSize)
.transactionally
).map( doSomething )...
I want to update this plain sql query with skipping the first N-th element.
But that is very DB specific.
Is is possible to get the pagination bit generated by Slick? [like for type-safe queries one just do a drop, filter, take?]
ps: I don't have the Schema, so I cannot go the type-safe way, just want all tables as Map, filter, drop etc on them.
ps2: at akka level, the flow.drop works, but it's not optimal/slow, coz it still consumes the rows.
Cheers
Since you are using the plain SQL, you have to provide a workable SQL in code snippet. Plain SQL may not type-safe, but agile.
BTW, the most optimal way is to skip N-th element by Database, such as limit in mysql.
depending on your database engine, you could use something like
val page = 1
val pageSize = 10
val query = sql"""
select #${onlyTheseColumns.mkString(",")}
from #${dbSource.table}
limit #${pageSize + 1}
offset #${pageSize * (page - 1)}
"""
the pageSize+1 part tells you whether the next page exists
I want to update this plain sql query with skipping the first N-th element. But that is very DB specific.
As you're concerned about changing the SQL for different databases, I suggest you abstract away that part of the SQL and decide what to do based on the Slick profile being used.
If you are working with multiple database product, you've probably already abstracted away from any specific profile, perhaps using JdbcProfile. In that case you could place your "skip N elements" helper in a class and use the active slickProfile to decide on the SQL to use. (As an alternative you could of course check via some other means, such as an environment value you set).
In practice that could be something like this:
case class Paginate(profile: slick.jdbc.JdbcProfile) {
// Return the correct LIMIT/OFFSET SQL for the current Slick profile
def page(size: Int, firstRow: Int): String =
if (profile.isInstanceOf[slick.jdbc.H2Profile]) {
s"LIMIT $size OFFSET $firstRow"
} else if (profile.isInstanceOf[slick.jdbc.MySQLProfile]) {
s"LIMIT $firstRow, $size"
} else {
// And so on... or a default
// Danger: I've no idea if the above SQL is correct - it's just placeholder
???
}
}
Which you could use as:
// Import your profile
import slick.jdbc.H2Profile.api._
val paginate = Paginate(slickProfile)
val action: DBIO[Seq[Int]] =
sql""" SELECT cols FROM table #${paginate.page(100, 10)}""".as[Int]
In this way, you get to isolate (and control) RDBMS-specific SQL in one place.
To make the helper more usable, and as slickProfile is implicit, you could instead write:
def page(size: Int, firstRow: Int)(implicit profile: slick.jdbc.JdbcProfile) =
// Logic for deciding on SQL goes here
I feel obliged to comment that using a splice (#$) in plain SQL opens you to SQL injection attacks if any of the values are provided by a user.
Currently using GORM to connect to two databases: POSTGRES AND sqlite (using a code switch to choose which one to use). I have a 2 database tables defined in my schema that look like this:
type TableClient struct {
Model
Synchronised bool
FacilityID string `gorm:"primary_key"`
Age int
ClientSexID int
MaritalStatusID int
SpecificNeeds []TableOptionList`gorm:"many2many:options_specific_needs"`
}
type TableOptionList struct {
ID int `gorm:"primary_key"`
Name string
Value string
Text string
SortKey int
}
Previously, I would preload related table with code like this:
var dbClient TableClient
Db.Where("facility_id = ? AND client_id = ? AND id = ?;", URLFacilityID, URLClientID, URLIncidentID).
Preload("ClientSex").
Preload("MaritalStatus").
Preload("CareTakerRelationShip").
Preload("HighestLevelOfEducation").
Preload("Occupation").
Preload("SpecificNeeds").
First(&dbClient)
Now that lookup fails with a syntax error and when I look at the SQL generated, it shows the following SQL is generated:
SELECT * FROM "table_option_lists" INNER JOIN "options_specific_needs" ON "options_specific_needs"."table_option_list_id" = "table_option_lists"."id" WHERE (("options_specific_needs"."table_client_id","options_specific_needs"."table_client_facility_id") IN (('one','LS034')))
Pasting that into the sqlite console also fails with the same error: (near ",": syntax error)
The crux of your issue is in your WHERE clause, you need to use "OR", not ",".
This is likely an issue with GORM and you could open a GitHub issue with them for this. You can get around the issue using db.Raw() from GORM. In general, I prefer to avoid ORMs. Part of the reason is it is often easier to just build an SQL query by hand than try to figure out the strange way to do it in the ORM (for things beyond basic CRUD).
I am trying to write a configurable sql query executor using Slick. User provides a prepared statement with ? and at run time the exact query is formed by replacing ? with values.
Generally this is how one would run a plain sql query using slick.
val query = sql"#$queryString".as[(String,Int)]
In my case i would not know the result type so i want to get back a generic result type. Maybe a List of Tuples with each tuple representing a row of result SET.
Any ideas on how this would be done?
I found a solution from one of the scala git issues. Here it is
ResultMap extends GetResult[Map[String, Any]] {
def apply(pr: PositionedResult) = {
val resultSet = pr.rs
val metaData = resultSet.getMetaData();
(1 to pr.numColumns).map { i =>
metaData.getColumnName(i) -> resultSet.getObject(i)
}.toMap
}
and then we can simply do val query = sql"#$queryString".as(ResultMap)
Hope it helps!!
I am querying a MS SQL database using Linq and Entity Framework Code First. The requirement is to be able to run a WHERE SomeColumn LIKE '%sometext'clause against the table.
This, on the surface, is a simple requirement that could be accomplished using a simple Linq query like this:
var results = new List<MyTable>();
using(var context = new MyContext())
{
results = context.MyTableQueryable
.Where(x => x.SomeColumn.EndsWith("sometext"))
.ToList();
}
// use results
However, this was not effective in practice. The problem seems to be that the column SomeColumn is not varchar, rather it's a char(31). This means that if a string is saved in the column that is less than 31 characters then there will be spaces added on the end of the string to ensure a length of 31 characters, and that fouls up the .EndsWith() query.
I used SQL Profiler to lookup the exact sql that was generated from the .EndsWith() method. Here is what I found:
--previous query code removed for brevity
WHERE [Extent1].[SomeColumn] LIKE N'%sometext'
So that is interesting. I'm not sure what the N means before '%sometext'. (I'll Google it later.) But I do know that if I take the same query and run it in SSMS without the N like this:
--previous query code removed for brevity
WHERE [Extent1].[SomeColumn] LIKE '%sometext'
Then the query works fine. Is there a way to get Linq and Entity Framework to drop that N from the query?
Please try this...
.Where(x => x.SomeColumn.Trim().EndsWith("sometext"))
Just spoke to my colleague who had a similar issue, see if the following works for you:
[Column(TypeName = "varchar")]
public string SomeColumn
{
get;
set;
}
Apparently setting the type on the column mapping will force the query to recognise it as a VARCHAR, where a string is normally interpreted as an NVARCHAR.
I have a MySQL query that I use to retrieve random rows from a table. The query is:
SELECT * FROM QUESTION WHERE TESTID=1 ORDER BY RAND() LIMIT 10;
Now I need to change this query to Hibernate. Did a bit of googling but couldn't find the answer. Can someone provide help on this?
The random function is different between each underlying DB and is not a standard part of SQL92.
Given that you will need to implement a SQLDialect for the given database type you are using.
eg:
class PostgresSQLDialect extends org.hibernate.dialect.PostgreSQLDialect {
PostgresSQLDialect() {
super()
registerFunction( "rand", new NoArgSQLFunction("random", Hibernate.DOUBLE) );
}
}
Then you will need to define that dialect in the config
hibernate {
dialect='com.mycompany.sql.PostgresSQLDialect'
}
According to this post, you can do that :
String query = "from QUESTION order by newid()";
Query q = session.createQuery(query);
q.setMaxResults(10);
Not sure if it will work (especially for the random part), but you can try it :)